On a normal day, thirsty revelers easily drain two kegs of Guinness at Boston's Black Rose tavern. Come St. Patrick's Day — an official holiday in Bean Town — and they'll plow thorough 55 kegs.

“It's pretty crazy over there,” says Keenan Langlois, corporate chef for The Black Rose and the seven other restaurants in Boston's Glynn Hospitality Group. “People start early and spend all day there.”

And these days, not all of that Guinness is going down parched gullets. With what he says is the largest Guinness account in the state of Massachusetts, Langlois figured it was time to use it as an ingredient in food, too. His Black Rose burger stacks prime beef with Irish bacon, shredded cabbage and Guinness-spiked ketchup. And he's not alone.

Chefs have long known that the hearty Irish stout, brewed in Dublin since 1759, can add complexity to stews, soups, dips and even desserts. They use its bitterness and toasty malt flavor to offset rich, fatty meats, and echo its notes of chocolate and coffee in cakes and ice cream. Its creaminess offers a great platform for cheese, they say, especially Irish blues.

“It has a rich spectrum of uses,” says Paul Hartley, author of Guinness: An Official Celebration of 250 Remarkable Years. “It's this rounded velvety feel and it fuses with all the right things. Like oysters and blue cheese and chocolate. From time to time, I marinate chicken in Guinness and lime and grill it. It brings all that to life.”

Hartley's idea of the perfect St. Patrick's Day starts with Guinness-marinated Irish bacon, moves onto crepes with Guinness-poached mushrooms for lunch, and ends with a dinner of Irish “beef cobbler” — that is, Guinness-braised beef served with scones.

Pastry chef Alice Medrich would add dessert. Medrich has laced Guinness through chocolate cupcakes, reduced it to a syrupy essence, concocted creamy, egg-yolk-based ice cream from it, and made Guinness granita to scrape over vanilla ice cream. She sometimes uses it for the contrast of bitter and sweet, but also exploits its notes of coffee and chocolate to layer flavors. Exhibit No. 1? Her stout float with chocolate ice cream, chocolate syrup, and Kahlua.

“It's building the flavors,” says Medrich, author most recently of Sinfully Easy Delicious Desserts. “There's a lot of chocolate-coffee-malty things going on in the Guinness. The Kahlua picks up on the coffee notes in the Guinness. So everything's working together.”

That creaminess also makes it a good match for mild blue cheeses, Fletcher says, such as Ireland's soft, supple Cashel Blue. And though she says she prefers hoppier beers with cheddar, she admires the historic pairing.

“It's been the cornerstone of many a pub lunch for centuries,” she says. “There's the pleasure of knowing you're having a classic.”

Not everyone is enamored of Guinness. “It's just not very interesting,” Peter Begg, head of food development for Jamie Oliver Ltd. and a fan of craft beers, writes in an email. “It's OK to drink with oysters and to cook with a beef stew, but that's about it really.”

Perhaps it's a question of familiarity breeding comfort rather than contempt. Author Hartley loves it for its iconic status. And its longevity.

“Every time I go to a food exhibition and I see three- or four-thousand new products, the next year when I come back there will only be a few left,” he says. “But the Guinness will still be there.”

RECIPES

Caramelized Onion and Guinness Dip

1 tablespoon olive oil

2 large sweet onions, diced

1 cup cold Guinness

½ teaspoon salt

½ teaspoon ground black pepper

¼ teaspoon cayenne

1 pound extra-sharp cheddar cheese (preferably Irish), cubed

Crackers, chips or bread, to serve

In a large skillet over medium, heat the olive oil. Add the onions and cook, stirring occasionally, until browned and caramelized, about 20 minutes. If the onions begin to char before they caramelize, add a tablespoon or 2 of water. Set the onions aside and allow to cool.

Once the onions have cooled, in a food processor combine them, the Guinness, salt, pepper, cayenne, and cheddar. Pulse until combined and smooth. Serve with crackers, chips or bread. Also makes a great spread for a roast beef sandwich.

In a large stockpot over medium-high, bring the Guinness to a boil. Add the egg noodles and cook until al dente according to package directions. Drain the noodles, but reserve 3 cups of the liquid (add water if needed to have 3 cups). Set both aside.

Meanwhile, in a large, deep skillet over medium-high, combine the ground beef, onion, and garlic. Sauté until browned and cooked through, about 10 minutes. Add the flour and stir to coat. Stir in the mustard, Worcestershire sauce, thyme, and reserved Guinness. Cook for 5 minutes, or until the sauce has thickened. Season with salt and black pepper. Stir in the egg noodles and serve topped with scallions.